Lazio's fans have already been punished numerous times for racial behaviour. In 2013, they were charged four times by UEFA for racial offences during their Europa League fixtures with Tottenham Hotspur (home and away), Maribor and Borussia Monchengladbach, and they were forced to play two European games behind closed doors.

In August, their Champions League playoff match against Bayer Leverkusen was almost halted by referee Jonas Eriksson due to racist chants aimed at Leverkusen trio Jonathan Tah, Wendell and Karim Bellarabi, but they escaped punishment on that occasion.

Lazio coach Stefano Pioli, though, said stopping play on Wednesday night was not the right thing to do.

"If I had been the referee, I would not have stopped the game," he said. "Those chants should not be heard and there is no justifying it, but we've also got black players and they are respected.

"If we do this then you make a minority of people feel important. I would have let play continue."

Lazio's fans were also punished for racist insults towards M'Baye Niang and Edenilson in a Serie A fixture against Genoa a year ago, but their Nigerian midfielder Ogenyi Onazi says he does not notice them.

"When I am on the field, I don't hear what they are saying off it," he said. "Our fans are not racist, it's impossible."

Napoli goalkeeper Pepe Reina posted a picture of Koulibaly on Twitter and called for a "Stadio San Paolo which sends shivers down our spine on Sunday" against Carpi but added that it must also be "a respectful San Paolo."